Reusable Plastic Ammunition Casing

ABSTRACT

A reloadable plastic ammunition casing is provided for firearm use. The plastic casing is preferably constructed from currently available polymeric materials using plastic injection molding techniques. In the preferred embodiment the casing includes a cylindrical body having a top portion and a bottom portion. The top portion having an open end for receiving a propellant and a top lip for retaining a projectile. The bottom portion has an internal casing floor that includes at least one concentric step down towards a centrally located primer pocket such that an installed primer is located in blast communication with the concentric steps on the casing floor. The concentric steps uniformly disburse, distribute, and deflect the heat and gas pressures within the casing when fired, thereby avoiding structural failure, allowing for multiple reloads of a casing constructed entirely out of plastic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e)(1) to U.S. Ser. No. 61/955,105 filed Mar. 18, 2014, which is hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to ammunition casings, specifically casings constructed entirely of plastic materials or injection moldable non-metallic materials.

2. Background of Prior Art

Although the word bullet is often used synonymously with a cartridge, for the purposes of this disclosure the term bullet only refers to the projectile. The cartridge includes several discrete parts, a bullet, a primer, propellant, and a casing. The bullet acts as a projectile that shoots out of the firearm. The primer is a detonation cap located within the base of the cartridge, containing a compound that directionally detonates to ignite the propellant. The propellant is an explosive material, usually gunpowder that burns very quickly at extreme temperatures to create a massive increase in gas pressure to push the bullet out of the casing and down the bore of the firearm. The casing performs several functions, it acts as a vessel for the propellant, fixator for the bullet, secures the primer, contains the blast, and is usually made of brass. When the cartridge is fired, the primer is struck causing the primer to explode directionally forcing the blast into the propellant, which in turn combusts to make a larger explosion with the massive gas pressures necessary to project the bullet on its trajectory.

Brass mediums have been preferred in constructing cartridge casings due to the ready availability of brass, its strength, temperature stability, and durability that allows a brass cartridge to be reloaded several times. The downsides of brass include a relatively heavy weight, increasing cost of the raw material, and significant tooling is necessary to manufacture. Further, brass is often deformed after just one shot, requiring resizing if reloaded. A lighter, cheaper, and easier to manufacture casing would be preferred, if the beneficial characteristics of the brass casing could be achieved. Plastic type materials candidates having good structural strengths and high melting include nylons, polyethylene, polypropylene, and PET, and polyphenylene sulfide with a blend of fiberglass or polycarbonates. Thus a polymeric casing, or referred herein as a plastic casing, is a pursuit of many inventors worldwide, but to date, brass still is the standard material used to construct cartridge casings.

With regard to the plastic ammunition shell casings, the prior art tracks several inventive design paths, one path of developing an improved gas blast pressure absorbing plastic mediums to construct the casing is taught by Malikovic in U.S. Pat. No. 8.240,252, another path of developing an improved structural construct of the casing allowing the casing to be constructed in multi-components formed from existing plastic mediums as taught by Padgett in U.S. Pat. No. 8443730, and another path involving an integrally formed polymeric casing that is manufactured using injection molding processes is taught by Trivette in U.S. Pat. No. 8,186,273.

Following the path involving improved casing structures, inventor David Eduardovich Khvichia from Moscow identified the problem to be solved in application EP 1388726 A1, which was to increase structural strength of a plastic casing through structural design improvement, while maintaining a low price of manufacture in using common plastics and existing injection molding manufacturing techniques. Khvichia solution involved a plastic cartridge case in the shape of a thin-walled cup of cylindrical external surface and internal surface comprising three conical portions of length and taper increasing from the bottom having the opening for the primer with a dam-diaphragm separating the cartridge case part and the part for the primer installation. This two-part construction allowed each component to be integrally formed from existing plastic polymer mediums using common injection molding techniques, but required the marrying two or more discrete components together during assembly.

As discussed above, Padgett #730 provided a multi-component casing having concentric shoulders, with the topmost shoulder or neck being relatively thin and having an internal diameter defined by the projectile similar to other prior art examples of plastic casings. Padgett's shoulders concentrically expand uniformly under the gas pressures formed during firing, thereby alleging a smoother release of the projectile from the casing into the barrel of the firearm. The smoother the release of the projectile, the greater the accuracy. Padgett #730 further added longitudinal ribs that provide additional wall rigidity of the cartridge from top to bottom, while maintaining the concentric shape at the neck and bullet contact as much as possible. The ribs further provide improved flow during manufacture using the plastic medium during the molding process which is commonly known in the injection molding arts. Padgett does not teach an integrally formed casing constructed of a continuous flow of plastic medium able to be manufactured in a single shot injection process. Instead Padgett's design is limited to multi-components that rely upon ‘plastic welds’ that are expected to hold for just one shot, and would be unloadable thereafter. See Padgett U.S.Pat. No. 8,443,730 page 14, line 52 and page 15 line 5.

The integrally formed casing disclosed in Trivette #273 has a uniform thickness at the bullet receiving end, but the casing wall thickens towards the primer end, having a conical shape internally. This conical shape as disclosed on page 3 lines 10-20 is intended to direct a majority of the blast force toward the open projectile end, which per Trivette helps maintain the structural integrity of the lower portion of the casing during firing. However, the Trivette #273 design essentially shapes the lower portion of the casing like an upside down funnel with the small opening being at the primer. The lower portion is then partially filled with plastic, rather than allowing adequate space for propellant, thus limiting Trivette's casing application to limited propellant loads as used for blanks or target only. More importantly, Trivette's conical interior shape by it's design funnels the propellant blast forces up at the projectile end while directing equal but opposite forces down at the primer pocket. The projectile end is proximal to the thinnest part of the casing wall at the location where the projectile seats and is one of the common failures of plastic casings. Primer pocket failures are another common failure area of the plastic casting. The gas pressures at the primer pocket are greatly magnified by the nozzle like effect of the Trivette's conical interior that literally focusses the opposing blast forces within the casing directly at the primer, causing leak by or burn through of the primer to primer pocket seal.

This disclosure is for an improved structural construct for an integrally formed casing that is constructed from commercially available polymer plastic mediums, manufactured using common plastic injection molding techniques, having a consistent casing wall thickness from the projectile end to the primer end, resulting in a reloadable plastic casing that has equivalent internal space for propellant as a brass casing, without the cost or complexity of exotic polymer plastics or intricate manufacturing methods.

SUMMARY OF INVENTION

Applicants'plastic casings are provided for use in loading and reloading ammunition for revolver hand guns, rifles, semi-automatic and automatic weapons, and the like, in which the ammunition casing is made from a polymeric plastic material formed using plastic injection techniques. The inventive casing provides a reusable, light weight, nonmetal casing. The casing has internal stepped structure elements at it's lower portion that provide containment and uniform force dispersion without focussing the primer blast or the secondary propellant blast, resulting in the projectile to release without causing structural failure of the casing. The structural durability of the plastic casing after being fired allows for multiple reloads similar to a brass casing.

The plastic casing is manufactured by practicing proven injection molding techniques using commercially available plastic polymer based mediums. For the purposes of this disclosure, any injection moldable non-metallic materials suitable for constructs the casing is referred herein as plastic. Applicants'plastic casing being loadable and reloadable similar to brass, in that a primer cap is pressed into the primer aperture in the butt end of the casing, propellant is metered within the casing's body followed by the projectile being pressed into the casing opening completing the loading process.

Upon review of the following descriptions taken in combination with accompanying figures, it is contemplated that the instant plastic ammunition casings may be used and reused for many different purposes and firearm types, as well as for target practice rounds including use with wax or powder projectiles.

DETAILED DESCRIPTIONS OF THE FIGURES

FIG. 1 is an exploded diagrammatic perspective of the preferred embodiment of a integrally formed polymeric casing including a projectile, propellant, and primer;

FIG. 2 is a cutaway side view of the embodiment shown in FIG. 1; and

FIG. 3 is a top view of the embodiment shown in FIGS. 1 and 2.

DETAILED DESCRIPTIONS OF THE INVENTION

The preferred embodiment of the reloadable plastic casing 30 used for ammunition is shown in FIGS. 1-3. As depicted in FIG. 1 by exploded perspective view the integrally formed polymeric casing 30 is depicted with a propellant 15, a projectile 20, and a primer 10. The casing 30 has a hollow cylindrical body 32 with a top portion 50 and a bottom portion 60. The top portion 50 includes an open end 31 for receiving a propellant 15 and a top lip 31 sized and shaped for retaining a projectile 20 as seated on an internal shelf 35. The internal shelf 35 resists the setting of the projectile 20 too deep within the cylindrical body 32 when production loading or reloading. The bottom portion 60 of the cylindrical body 32 includes an internal casing floor 39 that comprises at least one concentric step 38 down towards a centrally located primer pocket 40.

The primer pocket 40 being constructed and arranged to retain a primer 10, such that when installed in the casing 30, the primer 10 is in blast communication with the concentric steps 38 at the casing floor 39 which deflects and disburses the primer blast A and propellant blast B (depicted by arrows in FIG. 2) into the interior of the cylindrical body 32 through a primer aperture 41. The concentric steps 38 being constructed and arranged so as to avoid focusing or funneling the gas pressures within the cylindrical body directly at the primer pocket 40.

The bottom portion 60 further includes a ring 34 around the exterior of the cylindrical body 32 that allows for extraction of the plastic easing 30 after being fired. The projectile 20 and primer 10 retention may be enhanced by using suitable sealant or glue (not shown).

As depicted in FIG. 1 and cutaway side view in FIG. 2 the propellant 15 locates within the plastic casing 30 above the concentric steps 38 and casing floor 39. Similar to a brass casing counterpart, the plastic casing 30 has substantially parallel walls along the cylindrical body 32 thus providing enough interior volume for full propellant 15 loads similar to a brass casing, overcoming the shortcomings of the plastic casing prior art. The casing floor 39 design provides the structural integrity to endure, contain, and direct both the primer blast forces A, which are followed by the propellant blast forces B as illustrated by arrows A and B respectively. The concentric steps 38 deflect and redirect the primer blast forces A exiting the primer aperture 41 across the bottom of the propellant 15. The primer blast forces A more evenly impact the bottom of the propellant 15, rather than focused at the center of the propellant 15 as when using conical or funnel like internal casing shapes. By first dispersing the primer blast A more evenly into the propellant 15, followed by directing the propellant blast B and gas pressures off the concentric steps 38 in many different force directions rather than just at the primer pocket 40, structural failures and primer 10 leak by when fired are avoided, thus allowing for reloads for the plastic casing 30.

In FIG. 3 is the casing embodiment of FIGS. 1-2 shown from a top down perspective depicting the concentric steps 38 at the casing floor 39 circumscribing and stepping up incrementally from the primer aperture 41. The number, size, angle, and shape of the concentric steps 38 depend on caliber, propellant load, projectile weight, and other variables for the particular casing application. As depicted in FIG. 2 and discussed above, the concentric steps 38 cause a disruption or multi-direction deflection in the primer blast force A followed by the propellant blast force B at the casing floor 39 level in many directions, rather than primarily in one direction. Another benefit of the concentric steps 38 involves the increase in surface area at the casing floor 39. The heat impact to the polymeric material is reduced per square inch by increasing the surface areas over which the blast forces are applied during firing.

As shown in FIGS. 1-3, the innovative approach here involves spreading the forces more evenly within the plastic casting 30 rather than directing blast forces back at the primer 10. When focused, the resulting propellant 15 blast forces tend to exceed the durability characteristics of currently available polymeric materials, resulting in the plastic casing structurally failing after one shot, making reloading unavailable. Added structure such as filled shapes, stiffeners, or ribs to the cylindrical body 32 wall interior above the casing floor 39 allow for plastic casings 30 that are easier to reload by hand. For example, filled shapes may be added to tune in the exact volume within the cylindrical body 32 to avoid a user putting too much propellant 15 in the casing, or adding stiffeners or ribs running along the inside of the cylindrical body 32 to prevent crushing of the plastic casting 30 while the user is loading or reloading projectiles 20. Internal strength adding structures could be appropriate in certain applications but are not necessary.

Many polymeric materials can be used to construct the disclosed casing design, to include those materials compounded from Ultem, polyethylene, polypropylene, PET polyester, or poly carbonate. This is not an inclusive list, as many suitable materials would involve blends or mixtures which are not identified, such as those materials that also include color, fibers, additives, or other plastic injection moldable amendments. The scope of the appended claims should not be limited to the materials or design elements disclosed herein describing or showing the one preferred embodiment. Unless specifically stated otherwise in this disclosure, all alternatives serving the same, equivalent or similar purpose may replace any or all of the preferred materials or elements disclosed herein. 

What is claimed is:
 1. A plastic ammunition casing comprising: a cylindrical body having a top portion and a bottom portion; the top portion having an open end for receiving a propellant and a top lip for retaining a projectile; the bottom portion having an internal casing floor, the casing floor comprises at least one concentric step down towards a centrally located primer pocket; the primer pocket being arranged to retain a primer in blast communication with the casing floor; and wherein the cylindrical body is injection formed as one continuous piece from a plastic material.
 2. The non-metallic ammunition casing in claim 1, wherein the top portion includes an internal shelf for seating a projectile.
 3. The plastic ammunition casing in claim 1, wherein the plastic material is selected from a medium group consisting of materials compounded from polyethylene, polypropylene, PET polyester, or poly carbonate.
 4. The plastic ammunition casing in claim 1, wherein the bottom portion further includes a ring around the exterior of the cylindrical body that is constructed and arranged to allow for extraction of the casing.
 5. The plastic ammunition casing in claim 1, wherein the plastic material is colored. 